Counting tube stepped according to potential differences on guide electrodes controlled by charging-discharging rc circuit



July 2, 1963 L. c. BURNETT 3,096,463

COUNTING TUBE sTEPPED ACCORDING TO POTENTIAL DIFFERENCES ON cuIDE ELECTRODES CONTROLLED BY CHARGING-DISCHARGING Rc CIRCUIT Filed July 51, 1961 Inventor LIONEL C. BURNETT M 7/ Attorneys United States Patent COUNTING TUBE STEPPED ACCORDING TO PO- TENTIAL DIFFERENCES ON GUIDE ELEC- TRODES CONTROLLED BY CHARGING-DIS- CHARGING RC CIRCUIT Lionel Clifford Burnett, Beeston, England, assignor t0 Ericsson Telephones Limited, London, England, a British company Filed July 31, 1961, Ser. No. 128,212 Claims priority, application Great Britain Aug. 16, 1960 1 Claim. (Cl. SIS-84.6)

The present invention relates to a device for controlling the stepping of the discharge in a multi-cathode discharge tube.

Multi-cathode discharge tubes are commonly used in counting circuits, and such tubes comprise a plurality of cathode electrodes arranged in a ring around a common anode electrode. In operation a discharge between the anode and one cathode is made to step on to the next adjacent cathode for each increase in the count. This stepping action is brought about by applying sequential electrical pulses to two guide electrodes placed between each pair of cathodes. These two electrodes are known as first and second guide electrodes respectively. Commonly all the first guide electrodes are connected together and all the second guide electrodes are connected together.

According to the present invention I provide an electric control device for controlling the stepping of the discharge in a multi-cathode discharge tube having first and second guide electrodes between each pair of cathode electrodes, which device comprises a transistor capable of conducting a current between its emitter and collector, means for applying a control pulse to the base of the transistor, a direct connection between the transistor collector and the first guide electrodes, and a further connection comprising a delay device between the transistor collector and the second guide electrodes.

The delay device includes a diode which has the eifect of preventing the resetting of the delay device by the transistor current and of ensuring that it is reset only by the tube discharge current.

One embodiment of the invention will now be described with reference to the drawing accompanying the specification, which shows an electric stepping control circuit for a counting tube according to the invention.

Referring now to the drawing, a control pulse appearing at terminal X is applied to the base of an NPN-type transistor T through an isolating capacitor C1 and resistor R1. A bias potential Vb is applied through a resistor R2 to the junction of C1 and R1. The emitter of the transistor is connected to a source of potential Ve, and the collector is connected through a limiting resistor R3 to a source of potential Vc. The collector is also connected directly to a first terminal A and through a resistor R4 in series with a diode D to a second terminal B. The diode D is connected so as to prevent the flow of current from the collector of the transistor through resistor R4 whilst permitting the flow of current in the opposite direction. A capacitor C2 is connected between terminal B and a source of potential V.

A gas-filled discharge tube V1 has its anode connected to a source of positive potential +HT through a resistor R5. Nine of the ten cathode electrodes are connected directly to the negative potential V, Whilst the tenth cathode is connected to the same potential through a resistor R6 in conventional manner. Ten first guide electrodes G1 are connected together and to terminal A, and ten second guide electrodes are connected together and to terminal B.

Consider now the instant when the discharge in the tube V1 is between the anode and cathode 1. Transistor T is non-conducting due to the negative bias potential -Vb, and thus terminal A is at potential Vc.

When a positive-going control pulse is applied to terminal X the transistor T is rendered heavily conducting, and the potential drop across resistor R3 reduces the potential of terminal A from V0 to almost Ve. This causes the discharge in the tube V1 to move from cathode 1 to the adjacent first guide electrode. At the same time capacitor C2 charges to approximately Ve through charging resistor R4 and diode D, thus delaying the fall of the second guide electrodes. R4 and C2 constitute a delay device since diode D is conducting.

On the termination of the control pulse transistor T cuts off and terminal A rises to potential Vc. Terminal B remains at potential Ve since diode D becomes nonconducting and prevents the flow of current from the transistor to re-charge the capacitor. Due to the difference in potential between the first and second guide electrodes the discharge in the tube is transferred from the first to the second guide electrode. The discharge current now charges capacitor C2, raising the potential of terminal B towards the anode potential of the tube. When the second guide electrodes become sufliciently positive with respect to cathode 2 in the tube the discharge transfers from the guide electrode to cathode 2, and capacitor C2 stops charging.

The above operations are repeated on the receipt of each successive control pulse, causing the discharge to move around the ring of cathode electrodes.

The control pulses may be derived from any suitable pulse source, including the output from another multicathode tube in the case of a counter comprising a number of such tubes connected in cascade.

It will be apparent that the higher the transistor working potential becomes, the faster will the discharge be transferred. Thus higher counting speeds may be attained by the use of high-voltage transistors.

Although in the above embodiment an NPN-type transistor is used, the use of a PNPtype transistor is not excluded, the potentials Vb, V0 and Ve being altered accordingly. In such a case the transistor would be normally conducting, and the applied control pulse would cut ofi the transistor and thereby cause a drop in the potential of the collector.

I claim:

In an electric control circuit for controlling the stepping of the discharge in a gas-filled discharge tube of the type having an anode electrode connected to a source of positive potential, a plurality of cathode electrodes connected to a source of negative potential, at least one of said cathode electrode connections including a resistor, and a first and a second guide electrode located between each pair of adjacent cathode electrodes, all of said first guide electrodes being connected together to a first terminal and all of said second guide electrodes being connected together to a second terminal, the combination of:

(1) an anode resistor connected in the discharge current path of said discharge tube;

(2) a transistor having collector, emitter and base electrodes so connected to suitable sources of potential that said transistor is capable of conducting a current between said collector and emitter electrodes;

(3) Means for applying a control pulse to the base electrode of said transistor, said means being so constructed and arranged that the potential of the collector electrode falls on the application of said control pulse to said base electrode and that said collector potential is restored on the termination of said control pulse;

(4) a direct connection between said collector electrode and said first terminal; and

(5) a delay device comprising a delay resistor and a diode connected in series between said collector electrode and said second terminal and a capacitor connected between said second terminal and said source of negative potential;

(6) said diode being so poled that the change in potential of said second terminal resulting from the application of a control pulse to the base electrode of said transistor is delayed by a time dependent upon the current flowing through said delay resistor, and 10 that the change in potential of said second terminal resulting from the termination of said control pulse is delayed by a time dependent upon the current flowing to said second terminal through said anode resistor and the discharge path of said discharge tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,966,613 Chao Dec. 27, 1969 

